Analysis of volatile organic compounds in water and air using attapulgite clays

Abstract

The purge and trap procedure commonly used for analysis of volatile organic compounds in water or air can be significantly improved using traps employing clays and modified clays as adsorbents. Examples of clays include attapulgite clay, attapulgite clay modified with tetrasodiumpyrophosphate, carboxymethylcellulose and the combination thereof, kaolin clay, kaolin clay modified with tetrasodiumpyrophosphate, carboxymethylcellulose or the combination thereof, and mixtures of the above clays.

What is claimed is: 
     
       1. A method of sequential adsorption, storage, and desorption of a multiplicity of organic compounds contained in a gas stream at concentrations from about 0.5 parts per billion to about 100 parts per million with retention of the relative proportions of each of said organic compounds in each of the adsorption, storage, and desorption cycles comprising flowing said gas stream through an adsorbent bed comprising a clay to adsorb said organic compounds in amounts which are the same proportionate portion as each are found in said gas stream, storing the adsorbed organic compounds in the clay, desorbing said organic compounds in substantially the same proportionate portion as each are stored in the clay at a temperature between about 50° C. and about 600° C. for a time sufficient to desorb organic compounds, and removing residual organic compounds from the clay by heating the clay in a flowing gas at a temperature of at least 450° C. for a time sufficient to remove residual organic compounds from the clay. 
     
     
       2. The method of claim 1 wherein the clay is selected from the group consisting of attapulgite clay, attapulgite clay modified with tetrasodiumpyrophosphate, carboxymethylcellulose, and the combination thereof, kaolin ciay, kaolin clay modified with tetrasodiumpyrophosphate, carboxymethylcellulose, and the combination thereof, and mixtures thereof. 
     
     
       3. The method of claim 1 further characterized in having a water removing adsorbent placed upstream of the clay adsorbent bed. 
     
     
       4. The method of claim 1 further characterized in that the clay is present in combination with another adsorbent bed containing adsorbent selected from the group consisting of silicalite, dealuminated zeolite Y, and fumed silica.